American Megatrends MegaRAID Express 500 - Manual (Page 27)

Chapter 2 Introduction to RAID 13
Hot Spares
A hot spare is an extra, unused disk drive that is part of the disk subsystem. It is
usually in standby mode, ready for service if a drive fails. Hot spares permit you
to replace failed drives without system shutdown or user intervention.
MegaRAID Express 500 implements automatic and transparent rebuilds using
hot spare drives, providing a high degree of fault tolerance and zero downtime.
The MegaRAID Express 500 RAID Management software allows you to specify
physical drives as hot spares. When a hot spare is needed, the MegaRAID
Express 500 controller assigns the hot spare that has a capacity closest to and at
least as great as that of the failed drive to take the place of the failed drive.
Important
Hot spares are employed only in arrays with redundancy, for
example, RAID levels 1, 3, 5, 10, 30, and 50.
A hot spare connected to a specific MegaRAID Express 500
controller can be used only to rebuild a drive that is
connected to the same controller.